Electric lamp with integral support



May 10, 1966 D. R. DAYTON ETAL 3,250,939

ELECTRIC LAMP WITH INTEGRAL SUPPORT Filed Dec. 5, 1962 DAVID R. DAYTON JULIAN J. WlERZBlCKl INVENTORS ATTORNEY United States Patent This invention relates to electric lamps, and particular- I 1y to those of the incandescent type having built in reflectors, it is also useful in other types.

Incandescent lamps are sometimes made in which an electrically-heated filament is enclosed in a glass bulb having a bowl-shaped portion and a cover plate, the two being sealed together at their outer circumferences to form a single bulb. A reflective coating of metal or dichroic material is generally present on the inside surface of the bowl-shaped portion, generally called simply the bowl, with an incandescible coiled filament in position such that some of the light from it will fall on the reflector and be reflected out of the bulb. During operation the bulbs of such lamps generally blacken considerably, due to evaporation of the filament material, thereby reducing the light output of the device. Nonetheless, a lamp of this type is desirable for many purposes and especially for use in photographic projection apparatus using a large lens.

The blackening can be greatly reduced, and the lamp made suitable for projection and other purposes, if a portion of the bulb is enlarged, and especially if it is enlarged in the region where the cover plate is sealed to the bowl of the device, that is, between the bowl and the cover plate. The blackening will then deposit mainly on the interior surface of the enlarged portion, which runs cooler than the rest of the bulb, thereby keeping the lightreflecting and light-transmitting portions clear. As a result, a very eflicient projection lamp is produced.

A lamp used in a projector is generally operated a a high filament temperature and so has a limited life and must be replaced from time to time. In order to avoid the inconvenience of having to re-align the projector every time the lamp is changed, it is desirable to have some fixed reference member in the lamp envelope, with respect to which the alignment of reflector and filament can be fixed, and which will seat against a reference member in the projector, with respect to which member all optical parts in the remainder of the projection system are fixed. Then when the reference member in the lamp is seated against the reference member in the projector, accurate alignment and proper focus is assured.

The back of the enlarged portion of the bulb can be made substantially flat, like a flange around the edge of the bowl, and can then be used as the desired reference member. However, we have discovered that thealignment can be facilitated by aflixing a flat annular metal ring to the flat flange portion of the bulb, and arranging a socket in the projection equipment to have a corresponding flat portion against which the fiat annular metal ring can seat, and with respect to which the optical system is aligned.

Moreover, the flat annular metal ring can have one or more arms extending from it, and in a predetermined position with respect to the combination of filament and reflector, the arms being designed to engage with a socket in such a manner as to fix the orientation of the filament and reflector in a plane perpendicular to the bulb axis, when in the socket. The socket will be fixed in position with respect to the optical system with which the lamp is to be used, so that the lamp will be properly aligned with the system in all necessary directions.

We have further discovered that the fiat annular metal ring should be aflixed to the flat portion of the lamp by a layer of a resilient cement, such as a rubber cement, in order to avoid strains in the glass.

Other objects, advantages and features of the invention will be apparent from the following specification taken in connection with the accompanying description, in which:

FIG. 1 is a perspective view of a lamp according to the invention; and

FIG. 2 is a profile cross-section of said lamp and of the socket or bulbs for the lamp.

In FIG. 1, the lamp bulb 1 comprises the cover plate 2, the rim 3, flat flange 4, and bowl 5, the lead-in seal chamber 6, and the sealed exhaust tube 7. A cylindrical metal base cup 8 is aflixed to the apex of bowl 5, through a flange 9 provided on the cylindrical base cup 8 for the purpose, and the cement 23 contact pins 10, 11 extend through the bottom of the cup 8, being insulated from the metal thereof by bushings or the like. The lead-in wires 12, 13, which extend through the seal chamber 6, are connected to said contact pins 10, 11, lead-in wire 12 to contact pin 10, and wire 13 to pin 11.

Inside the lamp the lead-in wires extend upward to support the electrically-conductive fialment coil 14, which canbe of suitable material, for example tantalum carbide or tungsten. The coil can be wound to square crosssection, as shown, or can be of some other suitable form, such as a coiled-coil. The lead-in wires 12, 13, are supported at their upper ends by passing through a glass button 15 on the ends of exhaust tube 7. A coating of reflecting material is present on the inner surface of the bowl 5, and flange 4, and extends part way up on rim 3. The reflecting material can be, for example, aluminum or a dichroic material, the latter being a series of alternate coatings of different materials, such as magnesium fluoride and zinc sulfide, as is now well known.

The bulb is usually filled with a gas inert with respect to the filament such as argon, at a high pressure, preferably above atmospheric.

The annular metal ring 17, having the outwardly extending arms 18, 19 diametrically opposite each other, is afiixed to the outside surface of glass flange 4 by the resilient cement layer 20, as shown in FIG. 2. A silicone rubber cement is especially effective, for example, sold under the trademark Silastic RTV 891, made by the Dow Corning Corporation. That figure also shows the flat metal plate 21, having an opening 22 through which the bowl 5 can extend, the opening being slightly larger than the outside diameter of the bowl. The flat annular metal ring 17 seats flatly against the metal plate 21 around the opening 22, and the arms 18 and 19 extend outwardly along the plate, having radially slots 24, through which a stud 25 fits to secure the arms to the flat plate 21 in a fixed position. The stud 25 has a head 26, with a coiled spring around the stud, between said head and the flat plate to urge them apart, thereby forcing the flat plate 21 against the arm 18, the cotter pin 27 holding the arm against the action of the spring. In this way, the bulb is held firmly in the position for which it was aligned.

The flat plate 21 and the slots 24 can be aligned with an optical system, so that when the lamp is inserted through the plate and held fast, it will also be in proper alignment with the optical system. Connection to the contact pins 10, 11 can be made in any convenient manner, for example by flat contact springs bearing against them.

What we claim is:

' 1. An electric lamp comprising an enclosing glass envelope having a bowl portion and a cover plate, with a rim portion and a flat flange portion therebetween, a light source in said envelope, a substantially flat annular metal 3. An electric lamp comprising an enclosing glass envelope having a bowl portion and a cover plate, with a rim portion and flat flange portion therebetween, an electrically-conductive coil filament in saidenvelope, a substantially flat annular metal plate, and a resilient cement affixing said flat annular metal plate to said flange portion on the outside of said envelope.

4. An electric lamp comprising an enclosing glass envelope having a bowl portion and cover plate, with a rim portion and a flat flange portion therebetween, an electrically-conductive coil filament in said envelope, a

reflecting coating on a bowl portion of said envelope to reflect light from said filament, a substantially flat annular metal plate, and a resilient cement aflixed said flat annular metal plate to said flange portion on the outside of said envelope.

References Cited by the Examiner UNITED STATES PATENTS GEORGE N. WESTBY, Primary Examiner.

P. C. DEMEO, Assistant Examiner. 

4. AN ELECTRIC LAMP COMPRISING AN ENCLOSING GLASS ENVELOPE HAVING A BOWL PORTION AND COVER PLATE, WITH A RIM PORTION AND A FLAT FLANGE PORTION THEREBETWEEN AN ELECTRICALLY-CONDUCTIVE COIL FILAMENT IN SAID ENVELOPE, A REFLECTING COATING ON A BOWL PORTION OF SAID ENVELOPE TO REFLECTING COATING ON A BOWL PORTION OF SAID ENVELOPE NULAR METAL PLATE, AND A RESILIENT CEMENT AFFIXED SAID FLAT ANNULAR METAL PLATE TO SAID FLANGE PORTION ON THE OUTSIDE OF SAID ENVELOPE. 